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By the end of this section, you will be able to:
  • Discuss the components that make up the thoracic cage
  • Identify the parts of the sternum and define the sternal angle
  • Discuss the parts of a rib and rib classifications

The thoracic cage (rib cage) forms the thorax (chest) portion of the body. It consists of the 12 pairs of ribs with their costal cartilages and the sternum ( [link] ). The ribs are anchored posteriorly to the 12 thoracic vertebrae (T1–T12). The thoracic cage protects the heart and lungs.

Thoracic cage

This figure shows the skeletal structure of the rib cage. The left panel shows the anterior view of the sternum and the right panel shows the anterior panel of the sternum including the entire rib cage.
The thoracic cage is formed by the (a) sternum and (b) 12 pairs of ribs with their costal cartilages. The ribs are anchored posteriorly to the 12 thoracic vertebrae. The sternum consists of the manubrium, body, and xiphoid process. The ribs are classified as true ribs (1–7) and false ribs (8–12). The last two pairs of false ribs are also known as floating ribs (11–12).

Sternum

The sternum is the elongated bony structure that anchors the anterior thoracic cage. It consists of three parts: the manubrium, body, and xiphoid process. The manubrium    is the wider, superior portion of the sternum. The top of the manubrium has a shallow, U-shaped border called the jugular (suprasternal) notch    . This can be easily felt at the anterior base of the neck, between the medial ends of the clavicles. The clavicular notch    is the shallow depression located on either side at the superior-lateral margins of the manubrium. This is the site of the sternoclavicular joint, between the sternum and clavicle. The first ribs also attach to the manubrium.

The elongated, central portion of the sternum is the body. The manubrium and body join together at the sternal angle    , so called because the junction between these two components is not flat, but forms a slight bend. The second rib attaches to the sternum at the sternal angle. Since the first rib is hidden behind the clavicle, the second rib is the highest rib that can be identified by palpation. Thus, the sternal angle and second rib are important landmarks for the identification and counting of the lower ribs. Ribs 3–7 attach to the sternal body.

The inferior tip of the sternum is the xiphoid process    . This small structure is cartilaginous early in life, but gradually becomes ossified starting during middle age.

Ribs

Each rib is a curved, flattened bone that contributes to the wall of the thorax. The ribs articulate posteriorly with the T1–T12 thoracic vertebrae, and most attach anteriorly via their costal cartilages to the sternum. There are 12 pairs of ribs. The ribs are numbered 1–12 in accordance with the thoracic vertebrae.

Parts of a typical rib

The posterior end of a typical rib is called the head of the rib    (see [link] ). This region articulates primarily with the costal facet located on the body of the same numbered thoracic vertebra and to a lesser degree, with the costal facet located on the body of the next higher vertebra. Lateral to the head is the narrowed neck of the rib    . A small bump on the posterior rib surface is the tubercle of the rib    , which articulates with the facet located on the transverse process of the same numbered vertebra. The remainder of the rib is the body of the rib    (shaft). Just lateral to the tubercle is the angle of the rib    , the point at which the rib has its greatest degree of curvature. The angles of the ribs form the most posterior extent of the thoracic cage. In the anatomical position, the angles align with the medial border of the scapula. A shallow costal groove    for the passage of blood vessels and a nerve is found along the inferior margin of each rib.

Rib classifications

The bony ribs do not extend anteriorly completely around to the sternum. Instead, each rib ends in a costal cartilage    . These cartilages are made of hyaline cartilage and can extend for several inches. Most ribs are then attached, either directly or indirectly, to the sternum via their costal cartilage (see [link] ). The ribs are classified into three groups based on their relationship to the sternum.

Ribs 1–7 are classified as true ribs    (vertebrosternal ribs). The costal cartilage from each of these ribs attaches directly to the sternum. Ribs 8–12 are called false ribs    (vertebrochondral ribs). The costal cartilages from these ribs do not attach directly to the sternum. For ribs 8–10, the costal cartilages are attached to the cartilage of the next higher rib. Thus, the cartilage of rib 10 attaches to the cartilage of rib 9, rib 9 then attaches to rib 8, and rib 8 is attached to rib 7. The last two false ribs (11–12) are also called floating ribs    (vertebral ribs). These are short ribs that do not attach to the sternum at all. Instead, their small costal cartilages terminate within the musculature of the lateral abdominal wall.

Chapter review

The thoracic cage protects the heart and lungs. It is composed of 12 pairs of ribs with their costal cartilages and the sternum. The ribs are anchored posteriorly to the 12 thoracic vertebrae. The sternum consists of the manubrium, body, and xiphoid process. The manubrium and body are joined at the sternal angle, which is also the site for attachment of the second ribs.

Ribs are flattened, curved bones and are numbered 1–12. Posteriorly, the head of the rib articulates with the costal facets located on the bodies of thoracic vertebrae and the rib tubercle articulates with the facet located on the vertebral transverse process. The angle of the ribs forms the most posterior portion of the thoracic cage. The costal groove in the inferior margin of each rib carries blood vessels and a nerve. Anteriorly, each rib ends in a costal cartilage. True ribs (1–7) attach directly to the sternum via their costal cartilage. The false ribs (8–12) either attach to the sternum indirectly or not at all. Ribs 8–10 have their costal cartilages attached to the cartilage of the next higher rib. The floating ribs (11–12) are short and do not attach to the sternum or to another rib.

Questions & Answers

Description of menestraul cycle
Amos Reply
what is the anatomy
FAKE Reply
Anatomy is study of structure of organs.
Sneha
thanks
FAKE
The scientific study of the structure of human or animal bodies.
FAKE
I was confused as to which one would be right and I asked
FAKE
My answer and you answer both are right.
Sneha
i want to improve my study i like this app i interest physiology and anatomy
Su Reply
I also like this app am really interested in learning anatomy and physiology.
Johny
I have this book with my anatomy class it's awesome! also if look at crashcourse anatomy on you tube!
AMY
what the name
isaiah
umesh. rede
Rede
what is heart and long type answer
Lalita Reply
its a organ in the body
ay
describe about hear chambers.. valves.. arteries.. veins.. circulation.. inferior/superior venacava, aorta., tricuspid valve, mitral valve. pulmonary artery/vein, how oxigenation occur,systolic presure diastolic pressure.. stroke volume,cardiac output, ets.. heart located in which place, describe it
Sanjith
if you describe what I cited up, thogh you can write a long type answer about heart
Sanjith
autonomic functions took over
Vanarith Reply
What did they take over?
Eric
what is the average volume of blood in men and why does it varrie from women?
Esther Reply
what is the average volume of blood in men
Esther
5to6liter
Sarita
5to6liter dt
Sarita
umesh. rede
Rede
what is the definition of anatomy
Noriah Reply
Search google
killer
^of
chieng
The study of the structure or internal workings of something. "Machiavelli's anatomy 
Eric
post. communi. artey... this may be true 70% hope correct
vikash Reply
what is the strongest muscle in the human body?
Robiam Reply
masseter muscles
Om
yes masseter..... jaw muscle is the strongest muscle..
Sarita
Kidneys have direct effect on which
The function the loop
function of the loop?
Eric
the function of the loop of henle is to increase surface area for reasorbtion.
Conan
what is an atom and it's functions
Jany
An atom is the basic building block of matter.
Eric
which is the largest digestive gland in our body
Shubu
stomach
Barbara
What is the smallest bone in the body of the human being?
Kelvin
pisiform
Chulit
how many found in the head
obakunmi
4
ayesha
I think stapes is the smallest bone in human body
Sanjith
22
Sanjith
yes stapes is the smallest bone of our body
Sarita
the smallest bone is stapes in the ear
Isaac
smallest bone in human body is stapes or stirrup present in the middle ear ..
Om
stapes yes
Robiam
blood work and purification and it leads to cardiac systen
vikash
explain function of kidney
Noel Reply
filtration
Naqash
Secretagogue hormones
Sa
Organising water
Sa
hi
Jany
they help in the reproduction of sperms
Jany
Their main job is to cleanse the blood of toxins and transform the waste into urine. The kidney have several functions though. I think it is important to know them, but not in depth. But to truly understand the kindney's over all importance.
Eric
I meant to say the kidneys have.
Eric
how kidney help in reprdution of sperms?
Amir
the basic and functinal unit of kidney is Nephron
Sanjith
what us the name of the longest bone in the body
Ohuche Reply
femur
Zaini
femur
AKHILA
anatomical planes of the body
Opio Reply
sagittal plane, transverse plane and coronal plane
Ogechi
the only moveable bone in head
Sewar Reply
the only movable bone in head
Sewar
stapes. in the ear. but one could argue, all three ear bones move. malleus, Incas, and stapes.
Conan
mandible
Ankita
The mandible is.
Eric
The only unattached bone in the body is the hyod bone in the neck.
Eric
The mandible. It's the part that enables us to talk.
chieng
Mandible present in the head
Shubu
how can u protect ur self from corona
Nity Reply
how can u know that u have corona
Nity
with a test
Danielle
can protect by social distancing, following hand hygiene and standard precautions
Danielle
tq very much
sudhakar
as per the CDC incubation period 2 to 14 days. typical symptoms. typical symptoms, fever, cough, malagia, fatigue, and shortness of breath. alcohol based hand sanitizers. 60 to 85% strength, physical barriers, PPE. a face mask with three layers. Keep a physical distance of 6 feet or more.
Conan
a nasal swab test, or a blood test to confirm SARs-cov-19.
Conan

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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